The term “receive filter” is used interchangeably with “reception beamforming coefficient” or “reception beamforming weight” in the same meaning.
FIG. 1A illustrates a multi-antenna communication system having a transmitter with a plurality of transmit antennas and a receiver with a plurality of receive antennas. Referring to FIG. 1A, a base station (BS) transmitter 110 communicates with a receiver 120 with a plurality of (N) antennas.
The multi-antenna communication system seeks to increase spectral efficiency by establishing multiple links between a transmitter and a single user.
The transmitter applies beamforming weights to data that the receiver will receive through a plurality of antennas. To allow the receiver to detect accurate data through channel estimation for the respective antennas, the transmitter should transmit pilot subcarriers to which beamforming weights are applied on dedicated channels to the antennas of the receiver.
However, in a communication system designed share downlink pilot subcarriers among the antennas of the receiver, beamforming weights cannot be applied to the pilot subcarriers. Since the antennas of the receiver have different beamforming weights, the common use of pilot subcarriers with one beamforming weight at the antennas leads to inaccurate data detection.
Accordingly, there exists a need for an apparatus and method for transmitting and receiving a signal that enable accurate detection of data received at the antennas of the receiver in the case where pilot subcarriers to which different beamforming weights are applied with respect to the antennas of the receiver cannot be transmitted on dedicated channels, that is, in a communication system designed to share downlink pilot subcarriers among the antennas of the receiver. Also, there is a need for a subcarrier allocation structure that suits the transmission and reception apparatus and method.
FIG. 1B illustrates a multi-user, multi-antenna communication system having a transmitter with a plurality of transmit antennas and a plurality of receivers each having a plurality of receive antennas. The multi-user, multi-antenna communication system allows a plurality of receivers (i.e., mobile stations) to access the same resources simultaneously so that independent data streams flow between the transmitter and the receivers. That is, a BS transmitter 130 communicates with a plurality of receivers 140, 150 and 160 each having a plurality of antennas.
In the multi-user, multi-antenna communication system, the transmitter applies beamforming weights to data that the receivers will receive. In this case, the transmitter should transmit pilot subcarriers with beamforming weights with respect to the respective receivers. However, if the transmitter does not have a sufficient number of pilot subcarriers for the receivers as with Institute of Electrical Electronics Engineers (IEEE) 802.16 Partial Usage of SubChannels (PUSC) in which one pilot is shared among a plurality of receivers, beamforming weights cannot be applied to pilot subcarriers. Since the receivers have different beamforming weights, the common use of pilot subcarriers with one beamforming weight at the receivers leads to inaccurate data detection.
Therefore, there exists a need for an apparatus and method for transmitting and receiving a signal that enable accurate data detection in the communication system in which the transmitter does not use a sufficient number of pilot subcarriers for the receivers. Also, there is a need for a subcarrier allocation structure that suits the transmission and reception apparatus and method.
Even though dedicated channels are available for a plurality of pilot subcarriers, the resulting overhead is overwhelming. Thus, there exists a need for an apparatus and method for transmitting and receiving a signal, and a subcarrier allocation structure suitable for the apparatus and method, which reduce the overhead from transmitting pilot subcarriers on dedicated channels and also enable channel estimation at a receiver even though a match filter for an effective channel is not an optimal receive filter.